The present invention relates to an improved return lock device for a hand device for the transfer of a film from a backing strip to a substrate. More particularly, the present invention relates to a return lock that is integral with the applicator tip of the hand device.
A hand device for transferring a film from a backing strip to a substrate (alternately referenced herein as a xe2x80x9chand devicexe2x80x9d for the sake of convenience without intent to limit), is described in DE 42 20 712 C2. In this hand device, a supply spool and a take-up spool are rotatably mounted in a housing. A backing strip is wound on the supply spool, extends from the supply spool to an applicator tip arranged on the circumference of the housing, is wound around an application edge of the applicator tip projecting outwardly from the housing, and extends as far as the take-up spool. To transfer a film from the backing strip to a substrate, the hand device is manually gripped, pressed with the applicator tip against the substrate, and at the same time moved along the substrate so that the film adheres to the substrate as the backing strip is pulled away from the supply spool, runs around the application edge of the applicator tip, and is wound on to the take-up spool. A drive connection is provided or is operative between the supply spool and the take-up spool. On application of the torque transmitted by pulling off the backing strip on to the storage spool, the drive connection drives the take-up spool so that it takes up the backing strip at a speed which is greater than the speed of removal. A sliding clutch is provided between the supply spool and the take-up spool to guarantee that the speeds of supply and take-up are the same, and that a certain tension in the backing strip running on the take-up spool is not exceeded. Thus, tearing of the backing strip is prevented because of the sliding clutch. Here, the supply spool and the take-up spool can be arranged on a common axis of rotation, i.e., adjacent to each other. Alternatively, the supply spool and the take-up spool can be arranged axially parallel in the same circumferential plane of the backing strip, the take-up spool being arranged between the supply spool and the applicator tip.
In the hand device described in DE 42 20 712 C2, the drive connection between the supply spool and the take-up spool with integrated sliding clutch is formed by at least one pair of friction surfaces directly engaging each other, which surfaces are formed on opposing inner and outer sides of the disc-shaped spool walls. In order to guarantee rotary entrainment between the spools due to the friction acting on the frictional surfaces, a compressive stress is required for pressing the frictional surfaces against each other and prestressing them. In the hand device described in this publication, the compressive stress is generated in that at least one of the two frictional surfaces, preferably both surfaces, are formed on spool sections arranged flexibly transverse to the frictional surface concerned. The surfaces are prestressed against each other by a resilience, preferably by the spool walls themselves. The effectiveness of the rotary entrainment can be increased by engaging knobs or teeth with which the spool sections engage in each other. In this case, it is also possible that the spool sections may not be prestressed against each other, but that the rotary entrainment depends on at least one of the spool sections deviating laterally, elastically, and flexibly on mutual contact of the knobs or teeth, thereby generating a moment of resistance providing the basis of the rotary entrainment between the knobs or teeth.
A further problem with the mode of operation of existing hand devices is that both the supply spool and the take-up spool tend to run backwards somewhat after a rotary movement caused by removing the backing strip, such as a result of stresses on the backing strip. The reels reversing in this way can cause small loops which can impair the function of the hand device.
A hand device for transferring a film from a backing strip to a substrate may be provided with a return lock interacting with the take-up spool to prevent the backing strip from being pulled off the take-up spool and forming loops if the hand device is used incorrectly. In such design, the return lock is formed by a ratchet drive consisting of a toothed rim arranged on the circumferential edge of one of the winding spool walls. The rim interacts with a ratchet arm which extends sectionally to the tooth rim, and is resiliently loaded against the tooth rim so that if the direction of rotation coincides with the direction of the take-up spool, the ratchet arm runs over the tooth rim and blocks a return rotation of the take-up spool, and hence prevents looping of the backing strip in the opposite direction of rotation due to engagement in the tooth rim. The ratchet arm is connected by a plug pin connection to the lateral housing wall or the cover of the housing.
The hand device described in EP 0 606 477 A1 (corresponding to U.S. Pat. No. 5,430,904) exhibits a locking mechanism for locking the rotation of the supply spool when the hand unit is not in use. As in DE 42 20 712 C2, a backing strip extends from a supply spool, loops around an applicator tip, and extends as far as a take-up spool. The applicator tip is displaceably mounted between a retracted position of non-use and a released position of use. A ratchet arm extends from the inner end of the applicator tip to the periphery of the supply spool arranged behind the take-up spool, bypassing the take-up spool. Moreover, a stationary articulated section on the existing housing is arranged in such a position that when the applicator tip is displaced to its position of use the ratchet arm is laterally deflected to such an extent that it cannot interact with a tooth rim on the supply spool. When the applicator tip is moved to its position of non-use, the ratchet arm moves into its locking position interacting with the tooth rim on the supply spool. This known locking mechanism is capable of preventing looping of the backing strip in the non-operative position of the hand device. However, looping which occurs in the position of use, due to the intrinsic elasticity of the backing strip, for example, or due to movement of the hand device in the incorrect direction of movement, cannot be avoided with this hand device.
The present invention provides a simplified design of a hand device for transferring a film from a backing strip to a substrate with a return lock. Moreover, a hand device that is easy to install, is inexpensive to manufacture, and/or has as few components as possible, is to be provided. The locking device of the return lock or brake is formed by a component which extends integrally from the applicator tip, in the direction of an associated spool, and interacts with the applicator tip to execute a return lock. This design avoids the need for additional parts and allows simple manufacture, storage, and installation, thereby reducing production costs. The return lock or brake is able to interact with the supply spool or the take-up spool. This is possible because of the self-locking action of the drive connection between the spools.